Computed Tomography (CT) scans have become a cornerstone of modern medicine, offering doctors a powerful tool to peer inside the body and diagnose conditions ranging from cancer to internal injuries.
With their ability to produce detailed, three-dimensional images, CT scans have saved countless lives by enabling early detection and guiding critical treatments.
However, a groundbreaking study published in JAMA Internal Medicine in 2023 has sparked a sobering conversation about the potential risks of this widely used technology. The study projects that CT scans performed in the United States in 2023 alone could lead to approximately 103,000 future cancer cases, raising questions about how we balance the undeniable benefits of CT scans with their hidden dangers.
The Rising Use of CT Scans
The reliance on CT scans has surged in recent years. According to the JAMA Internal Medicine study, an estimated 93 million CT scans were performed on 62 million patients in the U.S. in 2023, a 30% increase since 2007.
This growth is driven by the technology’s versatility, speed, and accuracy, which make it indispensable in emergencies, cancer screenings, and diagnosing complex conditions like heart disease or kidney stones.
But this widespread use comes with a catch: CT scans expose patients to ionizing radiation, a known carcinogen that can damage DNA and increase the risk of cancer over time.
The study’s projections are striking. If current CT scan usage and radiation dosing practices continue, the researchers estimate that CT-related cancers could account for 5% of all new cancer diagnoses annually.
This places CT scans on par with other well-known cancer risk factors, such as alcohol consumption (5.4%) and excess body weight (7.6%). For context, about 2 million new cancer cases are diagnosed in the U.S. each year, meaning CT scans could theoretically contribute to 100,000 of those cases if trends persist.
How CT Scans Work and Why They Pose a Risk
CT scans work by combining multiple X-ray images to create a detailed, cross-sectional view of the body. Unlike traditional X-rays, which produce flat, two-dimensional images, CT scans capture hundreds of images as the machine rotates around the patient. This process relies on ionizing radiation, which carries enough energy to break chemical bonds in cells.
While low levels of radiation are generally considered safe, repeated or high-dose exposures can increase the likelihood of cellular damage that may lead to cancer years or even decades later.
The radiation dose from a single CT scan typically ranges from 1 to 10 millisieverts (mSv), compared to the average annual background radiation exposure of about 3 mSv from natural sources like cosmic rays. While this may seem small, the cumulative effect of multiple scans—especially for patients with chronic conditions requiring regular imaging—can add up.
The JAMA study used data from the University of California San Francisco (UCSF) International CT Dose Registry, analyzing trends from 2016 to 2022 to estimate the radiation doses delivered by 93 million scans in 2023. Their findings suggest that the risk is not uniform across all patients or scan types.
Who’s at Greatest Risk?
The cancer risk from CT scans varies depending on factors like age, sex, and the body part being scanned. Children and adolescents are particularly vulnerable because their developing cells are more sensitive to radiation, and they have a longer lifespan during which radiation-induced cancers may develop.
The study found that infants under one year old face a 10-fold higher risk of developing radiation-induced cancers compared to older age groups, with thyroid, lung, and breast cancers being the most common. For example, head CTs, frequently used to diagnose concussions or brain injuries in children, were identified as a significant contributor to cancer risk in this group.
Adults, who account for over 90% of CT scans, face the largest overall impact due to the sheer volume of scans performed. The study highlighted abdominal and pelvic CTs as the leading contributors to future cancer cases in adults, with lung, colon, bladder, leukemia, and breast cancers (in women) being the most frequently projected.
Women may be slightly more susceptible to certain cancers, such as breast and thyroid cancer, due to differences in tissue sensitivity.
Comparing Past and Present Estimates
The 2023 JAMA study builds on earlier research but paints a more alarming picture. A 2009 analysis estimated that CT scans performed in 2007 would lead to about 29,000 future cancers. The new estimate of 103,000 cases is more than three times higher, reflecting both the increased number of scans and improved methods for calculating organ-specific radiation doses.
Advances in risk modeling, based on data from atomic bomb survivors and other radiation-exposed populations, have allowed researchers to make more precise predictions about the long-term effects of CT scans.
However, it’s important to note that these projections are based on risk models, not direct evidence of causation. The American College of Radiology has emphasized that no study has definitively linked CT scans to cancer in humans, even among those who undergo multiple scans.
While the theoretical risk is grounded in the established link between ionizing radiation and cancer, proving a direct connection in individual patients remains challenging due to the long latency period of radiation-induced cancers and the influence of other risk factors.
The Life-Saving Benefits of CT Scans
Despite these concerns, CT scans remain a vital tool in modern medicine. They can detect life-threatening conditions like brain hemorrhages, pulmonary embolisms, or early-stage cancers, often before symptoms appear.
In emergencies, their speed and accuracy can mean the difference between life and death. For patients with chronic illnesses, regular CT scans can monitor disease progression and guide treatment plans, improving outcomes and quality of life.
The challenge lies in ensuring that CT scans are used judiciously. The JAMA study suggests that a portion of scans may be “low-value” or unnecessary, driven by factors like defensive medicine, patient expectations, or the profitability of imaging for healthcare systems.
Initiatives like Choosing Wisely, launched by the American Board of Internal Medicine Foundation, aim to reduce unnecessary imaging by encouraging doctors and patients to discuss the necessity of each scan and consider alternatives when appropriate.
Reducing the Risks: Practical Steps Forward
The good news is that there are ways to mitigate the risks associated with CT scans without sacrificing their benefits. Here are some key strategies:
- Optimize Radiation Doses: Radiologists can adjust scanner settings to deliver the lowest effective dose, particularly for children. The Image Gently and Image Wisely campaigns, supported by the American College of Radiology, promote dose optimization and provide resources for healthcare providers.
- Explore Alternatives: In some cases, radiation-free imaging options like MRI or ultrasound can provide similar diagnostic information. For example, MRIs are often used to evaluate brain or joint conditions, while ultrasounds are effective for assessing abdominal organs or pregnancies.
- Limit Unnecessary Scans: Doctors can use diagnostic checklists or algorithms to determine when a CT scan is truly needed. Educating patients about the risks and benefits can also help reduce demand for non-essential imaging.
- Adopt New Technologies: Emerging technologies like photon-counting CT scanners deliver lower radiation doses while maintaining image quality. These advancements could significantly reduce the cancer risk associated with CT scans in the future.
Patients can play a role too. If your doctor recommends a CT scan, ask questions: Is this scan necessary? Are there alternatives? Can the radiation dose be minimized? Keeping a record of your imaging history can also help you and your healthcare provider make informed decisions about future scans.
My Insights and Additional Findings
The balance between the benefits and risks of CT scans is both fascinating and complex. The JAMA study underscores the need for a cultural shift in how we approach medical imaging.
Too often, patients and even doctors view CT scans as a default solution, unaware of the cumulative risks. This is particularly concerning for younger patients, where the long-term consequences may not be immediately apparent.
One additional point worth noting is the global context. The U.S. performs far more CT scans per capita than many other developed countries. For example, a 2019 OECD report found that the U.S. conducted 245 CT scans per 1,000 people, compared to 151 in the UK and 138 in Germany. This suggests that cultural and systemic factors, like reliance on imaging for legal protection or patient reassurance, may be driving overuse in the U.S. Reducing unnecessary scans could align the U.S. more closely with international norms while lowering cancer risks.
Another consideration is the role of artificial intelligence (AI) in optimizing CT imaging. Recent studies, such as one published in Radiology in 2024, have shown that AI algorithms can enhance image quality from low-dose CT scans, allowing radiologists to use less radiation without compromising diagnostic accuracy. This technology is still evolving but holds promise for making CT scans safer in the years ahead.
Conclusion: A Call for Smarter Imaging
CT scans are a double-edged sword—lifesaving yet potentially harmful. The JAMA Internal Medicine study serves as a wake-up call, urging healthcare providers, patients, and policymakers to rethink how we use this powerful technology.
By prioritizing necessary scans, optimizing radiation doses, and embracing safer alternatives, we can ensure that CT scans continue to save lives without contributing to a hidden cancer burden.
The future of medical imaging is bright, with innovations like low-dose scanners and AI paving the way for safer practices. But for now, awareness and informed decision-making are our best tools. The next time you or a loved one faces a CT scan, take a moment to weigh the benefits and risks. It’s a small step that could make a big difference in the long run.